Schistosomiasis continues to be one of the leading public health problems in Asia. Until 1980, schistosomiasis in Asia was attributed in the medical literature to Schistosoma japonicum transmitted by the snail genus Oncomelania. Today, as a result of this NIH sponsored research, it is recognized that there is a S. japonicum species complex transmitted by a number of snail species of two diverging snail lineages. The snail species - Schistosoma sp. associations are phylogenetically constrained. This proposal continues to focus on uncovering the diversity of snails transmitting Schistosoma in Asia, with current emphasis in China. The objectives are 1) to continue detailed comparative anatomical studies of Pomatiopsidae: Triculinae snails throughout Southern China to establish clear definitions of genera and species, and to incorporate the new data into the phylogeny of the Pomatiopsidae thereby testing that phylogeny with each new addition. The snail-species-Schistosoma sp. interactions are mapped on the phylogeny to assess pattern and process of taxon- specific evolution and coevolution; 2) to continue molecular genetic studies of Triculinae taxa and populations of Oncomelania in laboratories established under this program in China. Molecular data are used to test the congruence of anatomy-based phylogeny with molecular-based phylogeny, and the pattern of snail genetics as it related to Schistosoma transmission; 3) to continue DNA sequence work in Philadelphia for phylogenetic assessment of the Pomatiopsidae. Work is in cooperation with the Institute of Parasitic Diseases, Shanghai, The Academy of Medical Sciences in Hangzhou, Zhejiang Province, China and Hubei Medical College. Molecular work in Handzhou focuses on Triculinae snails, while that in Shanghai is on Oncomelania throughout China relative to predicted regional differentiation of Schistosoma japonicum.